(a) Field of the Invention
The present invention relates to a manual valve of a hydraulic pressure control system for an automatic transmission, and in particular, to an improved manual valve capable of independently controlling all friction elements of the automatic transmission using an indirect control mechanism in which second stage control pressure is provided to the friction elements and a line pressure control solenoid valve.
(b) Description of the Related Art
Generally, a conventional automatic transmission for a vehicle includes a multi-stage gear shift mechanism connected to a torque converter, and a plurality of friction elements actuated by hydraulic pressure under control of a hydraulic pressure control system for selecting a gear stage of the gear shift mechanism.
In such automatic transmissions, the hydraulic pressure control system includes a pressure control means for controlling a level of hydraulic pressure generated by a hydraulic pump, manual and automatic shift control means for performing shift operation, hydraulic pressure control means for adjusting responsibility and shift quality by smoothing shift operation, distribution means for distributing the pressure from the hydraulic pressure control means to appropriate friction elements, and damper clutch control means for controlling operation of a damper clutch of a torque converter.
The gear shift control is achieved by the friction elements being selectively and differently applied by hydraulic pressure from the distribution means and cooperation of on/off and duty control solenoid valves, such that a constitution and control method of a hydraulic control system depends on particular power trains adapted by car makers and how the power trains are controlled.
The manual valve performs pressure line conversion by driver""s manipulation, and FIG. 4 shows a conventional manual valve adapted to the automatic transmission manufactured by the applicant of the present invention.
As shown In FIG. 4, a valve body is provided with a first port 200 for receiving hydraulic pressure from a hydraulic pump (not shown), a second port 202 for supplying the hydraulic pressure to a shift control valve (not shown) at ranges xe2x80x9cDxe2x80x9d, xe2x80x9c2xe2x80x9d, and xe2x80x9cLxe2x80x9d, a third port 204 for supplying the hydraulic pressure to a pressure regulator valve (not shown) at ranges xe2x80x9cNxe2x80x9d, xe2x80x9cDxe2x80x9d, xe2x80x9c2xe2x80x9d, and xe2x80x9cLxe2x80x9d, and a fourth port 206 for supplying hydraulic pressure to the regulator valve and an N-R control valve (not shown) at range xe2x80x9cRxe2x80x9d.
A valve spool 210 inserted into the valve body is provided with a connect part 212 formed at one end portion of the valve spool 210, a first land 214 positioned between the second and third ports at range xe2x80x9cP xe2x80x9d and positioned at the right side of the third port at other ranges, a second land 216 for communicating the third port 204 or the second and third ports 202 and 204 with the first port 200 at all ranges except for the ranges xe2x80x9cPxe2x80x9d and xe2x80x9cRxe2x80x9d, and a third land 218 for communicating the first port 200 and the fourth port 206 at the range xe2x80x9cRxe2x80x9d.
Also, the valve spool 210 is provided with a release opening 222 formed between the first and the second lands 214 and 216 and vertically passing through an axis of the valve spool 210, and a release hole 220 formed from the right end of the valve spool 210 to the release opening 222.
In this structure, the hydraulic pressure from the first port 200 is supplied to the third port 204 at range xe2x80x9cNxe2x80x9d, to the second and third ports 202 and 204 at range xe2x80x9cDxe2x80x9d, and to the fourth port 206 at range xe2x80x9cRxe2x80x9d, and the hydraulic pressure from the first port 200 is released via the release opening 222 and the release hole 220 at range xe2x80x9cPxe2x80x9d.
However, in this conventional manual valve, since the hydraulic pressure fed from the hydraulic pump is released at range xe2x80x9cPxe2x80x9d, the regulator valve ceases control such that the torque converter can receive only a small amount of hydraulic pressure through an orifice.
Accordingly, the lack of hydraulic pressure causes the friction elements to be damaged and delays hydraulic pressure supply to the friction elements particularly under sudden acceleration, resulting in. degraded sudden acceleration performance of the vehicle. Also, it is impossible to precisely measure the oil amount at range xe2x80x9cP.xe2x80x9d
Furthermore, this kind of manual valve can only be used in an automatic transmission because the pressure line conversions are performed at ranges of xe2x80x9cNxe2x80x9d, xe2x80x9cDxe2x80x9d, and xe2x80x9cR.xe2x80x9d
The present invention has been made in an effort to solve the above problems.
It is an object of the present invention to provide a manual valve of a hydraulic pressure control system capable of hydraulic control even at the range xe2x80x9cPxe2x80x9d, and preventing the friction elements from being damaged and avoiding sudden acceleration performance degradation because of the lack of oil.
It is another object of the present invention to provide a manual valve of the hydraulic pressure control system in which ranges can easily be modified from the 6 ranges of xe2x80x9cPxe2x80x9d, xe2x80x9cRxe2x80x9d, xe2x80x9cNxe2x80x9d, xe2x80x9cDxe2x80x9d, xe2x80x9c2xe2x80x9d, and xe2x80x9cLxe2x80x9d to the 7 ranges of xe2x80x9cPxe2x80x9d, xe2x80x9cRxe2x80x9d, xe2x80x9cNxe2x80x9d, xe2x80x9cDxe2x80x9d, xe2x80x9c3xe2x80x9d, xe2x80x9c2xe2x80x9d, and xe2x80x9cLxe2x80x9d.
To achieve the above object, a manual valve of a hydraulic pressure control system for an automatic transmission of the present invention comprises a valve body and a valve spool slidably inserted into the valve body, wherein the valve body is provided with a first port communicated with a regulator valve via a pressure line, a second port connected to a first pressure control valve and a second fail safe valve so as to supply hydraulic pressure thereto at range xe2x80x9cPxe2x80x9d, a third port connected to the regulator valve, an N-R control valve, and a first and a second switch valve so as to supply the hydraulic pressure from the first port thereto at range xe2x80x9cRxe2x80x9d, a fourth port connected to a second and a third pressure control valve and the first and second switch valves so as to supply the hydraulic pressure from the first valve thereto at ranges xe2x80x9c2xe2x80x9d, xe2x80x9c3xe2x80x9d, and xe2x80x9cDxe2x80x9d, and a fifth port connected to the first switch valve so as to supply the hydraulic pressure from the first port thereto at range xe2x80x9cLxe2x80x9d.